<h4>Tool</h4><table border="0"><tr><td valign="top"><b>Name</b></td><td valign="top">Multi-Scale Topographic Position Index (TPI)</td></tr><tr><td valign="top"><b>ID</b></td><td valign="top">28</td></tr><tr><td valign="top"><b>Author</b></td><td valign="top">O.Conrad (c) 2016</td></tr><tr><td valign="top"><b>Specification</b></td><td valign="top">grid</td></tr></table><hr><h4>Description</h4>Topographic Position Index (TPI) calculation as proposed by Guisan et al. (1999).

This implementation calculates the TPI for different scales and integrates these into one single grid. The hierarchical integration is achieved by starting with the standardized TPI values of the largest scale, then adding standardized values from smaller scales where the (absolute) values from the smaller scale exceed those from the larger scale. This integration scheme has been proposed by N. Zimmermann (<a href="http://www.wsl.ch/staff/niklaus.zimmermann/programs/aml4_1.html">toposcale.aml</a>).
<hr><h4>References</h4><ul><li><b>Guisan, A., Weiss, S.B., Weiss, A.D. (1999):</b> GLM versus CCA spatial modeling of plant species distribution. Plant Ecology 143: 107-122.</li><li><b>Weiss, A.D. (2000):</b> Topographic Position and Landforms Analysis. <a target="_blank" href="http://www.jennessent.com/downloads/tpi-poster-tnc_18x22.pdf">poster</a>.</li><li><b>Wilson, J.P. & Gallant, J.C. (2000):</b> Terrain Analysis - Principles and Applications.</li></ul><hr><h4>Parameters</h4><table border="1" width="100%" valign="top" cellpadding="5" rules="all"><tr><th>Name</th><th>Type</th><th>Identifier</th><th>Description</th><th>Constraints</th></tr>
<tr><th colspan="5">Input</th></tr><tr><td>Elevation </td><td>Grid (input)</td><td>DEM</td><td></td><td></td></tr><tr><th colspan="5">Output</th></tr><tr><td>Topographic Position Index</td><td>Grid (output)</td><td>TPI</td><td></td><td></td></tr><tr><th colspan="5">Options</th></tr><tr><td>Minimum Scale</td><td>Integer</td><td>SCALE_MIN</td><td>kernel radius in cells</td><td>Minimum: 1
Default: 1</td></tr><tr><td>Maximum Scale</td><td>Integer</td><td>SCALE_MAX</td><td>kernel radius in cells</td><td>Minimum: 1
Default: 8</td></tr><tr><td>Number of Scales</td><td>Integer</td><td>SCALE_NUM</td><td></td><td>Minimum: 2
Default: 3</td></tr></table>